Assessing net effect on emissions of implementation of Bus Rapid Transit system in São Paulo, Brazil: case study and some hypothetical scenarios
The paper investigates the relative influence of factors affecting vehicular emissions in high-flow BRT – Bus Rapid Transit corridors. Emissions were estimated using the IVE – International Vehicle Emission model, which bases estimates on the vehicle driving cycle, and the results of emissions measurements conducted by IPT – Institute of Technological Research of the State of São Paulo for different bus technologies and driving cycles. The developers of IVE have collected data about the technological characteristics of the fleet and driving cycles for different types of vehicles in São Paulo, Brazil. Data about operations in bus corridors in São Paulo was obtained from local transport agencies. Two types of analyses were conducted. First, a before and after analysis of a selected BRT corridor in São Paulo looked at the impacts on overall emissions. The results show that the comparison should not be restricted to the bus system only or to traffic in the specific road affected. When the contribution of autos taking alternative routes after the implementation of the BRT system is included in the estimates of total emissions, important changes in results can occur. A second analysis considered a number of hypothetical scenarios, simulating the impact of different variables related to system planning, design and operation, choice of technology and other general policies. The results indicate that vehicular emissions are influenced by a number of factors that, when combined, can bring favorable results, but that policies aimed at the automobile and consequences of BRT implementation on car users and car traffic are paramount.
Design of limited-stop services for an urban bus corridor with capacity constraints
In high-demand bus networks, limited-stop services promise benefits for both users and operators, and have proven their attractiveness in systems such as Transmilenio (Bogota, Colombia) and Transantiago (Santiago, Chile). The design of these services involves defining their itinerary, frequency and vehicle size, yet despite the importance of these factors for the network’s efficiency, no published works appear to provide the tools for designing high-frequency unscheduled services on an urban bus corridor, minimizing social costs.
This paper presents an optimization approach that minimizes these costs in terms of wait time, in-vehicle travel time and operator cost. Various optimization models are formulated that can accommodate the operating characteristics of a bus corridor, given an origin–destination trip matrix and a set of services that are a priori attractive. The models then determine which of these services should be offered at what frequencies and with which type of vehicles. A case study in which the model is applied to a real-world case of a bus corridor in the city of Santiago, Chile, is presented and the results are analyzed. Finally, the model is used on two different demand scenarios establishing which type of services tend to be good candidates on each case and providing preliminary insights on the impact of some key parameters.
On the development of public transit in large cities
This article presents a summary of the analyses and set of recommendations given by a committee of transit specialists gathered by the Minister of Transport of Chile aiming at improving Transantiago, the new transit system recently inaugurated for Santiago. This summary focuses on those recommendations directed towards improving the efficiency, service quality and sustainability of mass public transportation systems in major cities in the developing world and that could be implemented in a short term (within two years). Three broad dimensions of public transit are considered: competition and regulation; investment, financing, fares and subsidies; and the operation and use of infrastructure, design, inspection and control. Although the study grew out of the needs and characteristics of a city such as Santiago (Chile), and of the virtues and deficiencies of Transantiago, much of the analyses and recommendations could be adopted and implemented in the major cities of developed countries in Europe, North America and Asia.
Public transit corridor assignment assuming congestion due to passenger boarding and alighting
This paper proposes a formulation of deterministic equilibrium in a public transit corridor that takes into account the congestion effect as perceived directly in travel times. The identification of the relationship between flows and travel times includes time at transit stops for passenger boarding and alighting. A simple case is analyzed that demonstrates the existence of equilibria in which identical users adopt different travel strategies, and a method is supplied for determining such an equilibrium. To find the general case assignment for a corridor, an assignment algorithm based on incremental flow increases is also presented. Finally, the algorithm is implemented in a simple corridor. The results show that identical users faced with the same trip must be allowed to take different decisions for an equilibrium assignment to exist.
